The Development of Life & Atmospheric Change

How did the evolution of photosynthetic organisms change the atmosphere?

They increased oxygen and reduced carbon dioxide.

Why did oxygen accumulate slowly at first?

It reacted with iron and other substances before building up in the atmosphere.

What is oxidation?

A reaction involving the gain of oxygen or loss of electrons.

How did increasing atmospheric oxygen affect early anaerobic organisms?

Oxygen was toxic to many organisms adapted to oxygen-free environments.

Why did atmospheric oxygen support more complex life?

It enabled aerobic respiration, providing a more efficient way of releasing energy.

How did the formation of the ozone layer affect life?

It absorbed harmful ultraviolet radiation, making surface environments more suitable for life.

What is ozone?

A form of oxygen with the molecular formula O₃.

How is ozone different from ordinary oxygen gas?

Ozone is O₃, while oxygen gas is O₂.

Why is ozone important in the upper atmosphere?

It absorbs much of the Sun's harmful ultraviolet radiation.

How did increasing oxygen contribute to ozone formation?

Atmospheric oxygen allowed ozone to form through photochemical reactions.

Why is ozone near ground level considered a pollutant?

It can irritate the respiratory system and damage vegetation.

How did biological processes alter atmospheric composition?

Organisms carried out photosynthesis, respiration and carbon storage.

Why is the evolution of the atmosphere linked to the evolution of life?

Living organisms changed atmospheric gases, which in turn affected conditions for life.